Patent GB-910917-A (GB)
Title: Improvements relating to tempering sheet glass
Inventor: LONG BERNARD
IPC: C03B27/016
Filed: 1961-06-09
Abstract: 910,917. Tempering glass sheets. GLACES DE BOUSSOIS. June 9, 1961 [July 15, 1960; April 22, 1961], No. 20930/61. Class 56. In the tempering of plane glass sheets, a sheet is heated to softening temperature and introduced into the air gap between vertical faces of two thick cooling plates made of a material having a thermal diffusivity greater than 0.10 C.G.S. units and then rapidly bringing the plates up to the faces of the sheet until the thicknesses of the layers of air at atmospheric pressure on either side of the sheet are the same and less than thirty hundredths of a millimetre. Suitable materials are metals such as steels, brass, aluminium or copper or graphite or silicon carbide. Spacers placed between the sheet and the plates may be wire strip, pads or granules and are of material having a thermal diffusivity approaching that of air, i.e. of 0.18 C.G.S. units. Stainless steel is suggested for the wires or/pads and metals, metal oxides or mineral compounds for the granules. As shown in Fig. 1, a glass sheet 1 heated in a furnace 2 is lifted to position 11 between two cooling plates 3 which carry, in contact with their faces 4, calibrated metal wires 5 secured by their upper ends to the edges 6 of the plates and are tensioned by weights 7. The plates 3 are then rapidly moved into the positions 3<SP>1</SP> in which the wires, generally two, take up the positions 5<SP>1</SP> in contact with marginal zones of the sheet. As shown in Fig. 3, the sheet 1 is supported in a frame 14 on pads 15 and held vertical by two wires 17 which straddle the upper member 18 of the frame and are tensioned by weights 19. The wires 17 also act to space the sheet from the cooling plates 3 (not shown). The frame 14 is of less thickness than the glass sheet and is suspended by a flat rod 20 carried by the member 18. The sheet may also be suspended by a strip of less thickness than the sheet which extends around the two sides and base and is secured to a bar over and of less length than the top edge. Spacing wires may straddle the glass sheet as in Fig. 3 or may be secured to the plates 3. The sheet may be suspended and spaeed by a number of wires secured at their ends to common bars, the wires being passed under the sheet and the bars joined together for suspending with hooks. Calibrated grains 34 are caused to adhere to the plates 3 in Fig. 6a by spraying a jet from an atomizer charged with a liquid in which the grains are suspended and an adhesive is dissolved. Calcium carbonate grains in an aqueous solution of sodium silicate is suggested. For use when the sheet is suspended by tongs 9a, or held along its bottom edge, as in a suspended frame, the plates 3 are replaced by pairs of plates 3a, 3b, one pair of which, 3a, are moved first to grip lightly the sheet 1<SP>1</SP>, the suspending tongs 9 or holding frame lowered and the second pair of plates 3b are then moved to cover the top or bottom of the sheet. If necessary, to equalize the cooling effect, the wires 5b may be slightly less thick than the wires 5a. As shown in Fig. 13, in which tongs 9a are suspended in known manner and a rod 12a is raised to loosen their grip on the glass sheet 1<SP>1</SP>, the plates 3a are mounted for movement towards each other by curved plates 13a sliding on tubes 14a secured to the upper flanges 15a of I-irons 16a embedded in blocks 17a. The plates 3a also carry tubes 18a, sliding inside tubes 19a fixed to channel irons 20a, on which slide curved plates 21a on the upper plates 3b.